Lifecycle of a Tree

Lifecycle of Trees

How to Measure & ID

Week 1 Day 3

It is important that students understand the biology of trees to further be aware of trees’ role in the

ecosystem throughout its life.

Seedling

Seed

Sapling

Mature Oak

Snag

Background

Like all living things trees have a life cycle:BirthGrowthAgingDeath

As trees grow, their physical form changes as does their role in the forest ecosystem

Seeds

Seeds come in a variety of shapes, weights, colors, and sizes, depending on the species. Seeds develop from male and female parts of the trees

producing fruits. Some seeds are in a protective nut like an acorn

Others are in fleshy fruits, like the black cherry. The fruit of a pine is a cone and the seed is winged and resembles a

miniature helicopter when falling. Wind, water, animals, and people disperse seeds to the forest

floor, open fields, yards and roadsides. Where conditions are favorable for germination, seeds will

germinate and grow.

Which came first - the tree, or the seed?

Seedling The seedling grows and begins to develop

woody characteristics. The stems harden, change color, and develop

a thin protective bark. The stem may bend or develop branches that

reach toward light. Leaves or needles that develop are adapted to

shade, but lean or tilt toward light. Most roots are in the upper soil to absorb

water, nutrients and air. Seedlings compete for nutrients, water,

sunlight, and space. Threats include fire, flood, drought, disease,

insect attacks, and animals. At this stage the tree is most susceptible to

being killed.

Sapling When the tree is about 1-4 inches in

diameter at 4.5 feet, it is considered a sapling. standard height where tree’s diameter is

measured – diameter at breast height (DBH). As the tree starts to get taller the trunk

thickens and branches develop. A sapling is the size of a tree growing in a

nursery. In this juvenile state, the tree is not

mature enough to reproduce. Growing rapidly, the sapling has the same

competition and threats as seedlings.

Mature

With favorable conditions, a sapling will grow into a mature tree (>4 inches DBH).

During this stage, each tree will grow as much as its species and site conditions will permit.

In addition, flowers develop, reproduction ensues, fruits form, and seed dispersal can now occur.

Trees provide the maximum environmental benefits to people during this stage.

What does DBH mean?

What plant in the picture would you say is a

mature tree?

Decline• The life span of a tree is a wide-range, yet

death is inevitable. • A combination of factors overcome a tree and

causes it to die. – Injury, drought stress, followed by disease, rot,

root dieback, coupled with a lightning strike or insect infestation contribute to tree decline.

• Sometimes a single factor is serious enough to cause mortality.

Dead Tree Standing dead trees, called snags, play vital roles

in the life cycle of many organisms. A snag slowly breaks down and returns nutrients

as limbs, bark, and branches fall. It provides habitat and food for wildlife and insects.

Animals, insects, and fungi help break down the tree. Eventually, the snag will fall and return nutrients

to the soil where they are takenup by other trees. And, the cycle begins anew.

What stage of the lifecycle are these trees

in currently?

SEEDLING

What stage of the lifecycle are these trees

in currently?

SNAG

What stage of the lifecycle are these trees

in currently?

SAPLING